Combining Second-Order Jahn−Teller Distorted Cations to Create Highly Efficient SHG Materials: Synthesis, Characterization, and NLO Properties of BaTeM2O9 (M = Mo6+ or W6+)

Abstract

Two new oxides, BaTeMo₂O₉ and BaTeW₂O₉, have been synthesized, by standard solid-state techniques, that have strong SHG intensities of ∼600 × SiO₂, on the order of LiNbO₃. Both materials contain cations susceptible to second-order Jahn−Teller (SOJT) distortions, resulting in asymmetric coordination environments. The SOJT distortion polarizes the M⁶⁺−O and Te⁴⁺−O bonds. Equally importantly, these polarizations constructively add, resulting in the large SHG responses. Powder SHG measurements on BaTeM₂O₉ (M = Mo⁶⁺ or W⁶⁺) indicated that both materials are phase-matchable and have a 〈d_eff〉_exp of 28 and 22 pm/V, respectively. Using bond hyperpolarizability values (β's) of 130 × 10^-40 and 305 × 10^-40 m⁴/V for Te⁴⁺−O and Mo⁶⁺−O respectively, we calculate a 〈d_eff〉_calc of 20pm/V for BaTeMo₂O₉. In addition, through the powder SHG measurements, we are able to give a more reasonable value for β(W⁶⁺−O), 230 × 10^-40 m⁴/V. This value is consistent with the smaller polarizability and magnitude of the intra-octahedral distortion of W⁶⁺ compared with Mo⁶⁺.